Rfid devices using metamaterial antennas

ABSTRACT

A radio frequency identifier (RFID) tag can comprise an RFID chip, an antenna, and a feed line electrically coupling the RFID chip to the antenna. An encoded information reading (EIR) terminal can comprise a microprocessor, a memory communicatively coupled to the microprocessor, a communication interface, and an EIR device provided by a bar code reading device, an RFID reading device, or a card reading device. The RFID reading device can further comprise an antenna and a feed line. The antenna for the RFID tag or for the RFID reading device can be provided by a patch cell, a patch cell array comprising two or more patch cells, or by a patch cell stack comprising two or more patch cells. An equivalent circuit for the patch can comprise at least two inductances and a shunt capacitance. An equivalent circuit for the patch cell array can comprise two or more inductance groups connected via a series capacitance and two or more shunt capacitances. An equivalent circuit for the patch cell stack can comprises two or more capacitances connected via a series inductance and two or more shunt inductances. The antenna can have a composite right- and left-handed (CRLH) structure.

This is a Continuation of application No. 13/041,165 filed Mar. 4, 2011.The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The invention is generally related to RFID devices and is specificallyrelated to RFID tags and RFID readers using metamaterial antennas.

BACKGROUND OF THE INVENTION

Radio frequency identification (RFID) methods are widely used in anumber of applications, including smart cards, item tracking inmanufacturing and retail, etc. An RFID tag can be attached, e.g., to aretail item. An encoded information reading (EIR) terminal deployed atthe cashier's desk can be equipped with an RFID reader to read and/ormodify the memory of an RFID tag attached to a retail item.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a radio frequency identifier (RFID)tag comprising an RFID chip, an antenna, and a feed line electricallycoupling the RFID chip to the antenna. The antenna can be provided by apatch cell array comprising one or more patch cells, or by a patch cellstack comprising two or more patch cells. An equivalent circuit for thepatch cell array can comprise one or more inductance groups and one ormore shunt capacitances. An equivalent circuit for the patch cell stackcan comprises two or more capacitances connected via a seriesinductance, and two or more shunt inductances. The antenna can have acomposite right-and left-handed (CRLH) structure.

In another embodiment, there is provided an encoded information reading(EIR) terminal comprising a microprocessor, a memory communicativelycoupled to the microprocessor, a communication interface, and an EIRdevice provided by a bar code reading device, an RFID reading device, ora card reading device. The RFID reading device can further comprise anantenna provided by a patch cell array comprising one or more patchcells or by a patch cell stack comprising two or more patch cells. Anequivalent circuit for the patch cell array can comprise one or moreinductance groups and one or more shunt capacitances. An equivalentcircuit for the patch cell stack can comprises two or more capacitancesconnected via a series inductance, and two or more shunt inductances.The antenna can have a composite right- and left-handed (CRLH)structure.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 depicts a schematic diagram of an RFID tag;

FIGS. 2-4 depicts schematic diagrams and equivalent circuit diagrams ofvarious embodiments of antennas that can be used with an RFID tag orwith an RFID reading device;

FIG. 5 depicts am example of a graph of a composite left/right-handedphase constant;

FIG. 6 depicts examples of nested split ring resonators;

FIG. 7 depicts a network-level layout of a data collection systemutilizing EIR terminals;

FIG. 8 depicts component-level layout of an EIR terminal.

The drawings are not necessarily to scale, emphasis instead generallybeing placed upon illustrating the principles of the invention. In thedrawings, like numerals are used to indicate like parts throughout thevarious views.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment there is provided an RFID tag, schematically shown inFIG. 1. The RFID tag 101 can include an RFID chip 111 connected to anantenna 121 by a feed line 131. In one embodiment, feed line 131 can beprovided by a monopole. In another embodiment feed line 131 can beprovided by a micro metal stripe. In another embodiment feed line 131can be provided by a coaxial cable. In a yet another embodiment, feedline 131 can be provided by a twin parallel wire. In a yet anotherembodiment, feed line 131 can be provided by a coplanar waveguide.

In another aspect, RFID chip 111 and antenna 121 can be disposed withina housing 190. In one embodiment, the housing can have a form factordesigned to facilitate attaching the RFID tag 101 to an object to betracked (not shown in FIG. 1). In another embodiment, RFID chip, antenna121, and feed line 131 can be printed on a dielectric material.

In a further aspect, the physical dimension of an RFID tag can vary fromseveral millimeters to several centimeters.

In one embodiment, antenna 121 of RFID tag 101 can receive a signaltransmitted by an RFID reader (not shown in FIG. 1) and then cantransmit a response signal to be received by the RFID reader. Theresponse signal can contain useful data, e.g., a unique serial number ofthe RFID tag. In another embodiment, an RFID tag can constantly orperiodically transmit a signal irrespectively of receiving a querysignal from an RFID reader. In a yet another embodiment, an RFID tag caninitiate communications with an RFID reader.

In one embodiment, RFID tag 101 can be equipped with a battery (notshown in FIG. 1) that can be used to provide power to the RFID tag'scircuitry. In a further aspect, RFID tag 101 can include replaceablebattery or can be provided as a sealed unit. In one embodiment, an RFIDtag can be electrically connected to an external power source. An RFIDtag equipped with . a battery or connected to an external power sourcecan be referred to as an active RFID tag.

In another embodiment, RFID tag 101 can be devoid of a battery and canreceive power from an RFID reader. An RFID tag devoid of a battery canbe referred to as a passive RFID tag. The antenna of a passive RFID tagcan produce an electric current responsive to receiving a radiofrequency (RF) signal transmitted by an RFID reader. The electriccurrent produced by the antenna can be supplied to the tag's circuitry.In another embodiment, RFID tag 101 can receive one portion of its powerfrom a battery, while receiving another portion of power from anexternal power source.

Using active RFID tags provides many advantages as compared to passiveRFID tags. An active RFID tag can be read at larger distances ascompared to passive RFID tags, which typically can be read only at veryshort distances (up to several feet). An active RFID tag can initiatecommunications with an RFID reader. Active RFID tags usually supporthigher data bandwidth as compared to passive RFID tags.

On the other hand, an active RFID tag cannot function without battery orexternal power. An active RFID tag is typically more expensive tomanufacture. An active RFID tag is typically physically larger ascompared to passive RFID tags.

In a further aspect, RFID tag 101 can be used in a number ofapplications, including smart cards, item tracking in manufacturing andretail, etc.

A smart card is an identification card (e.g., a credit card, a passcard) which does not need to be swiped or otherwise physically contactedby a card reader. This capability can be implemented by placing an RFIDtag in the card.

Item tracking can be implemented by placing an RFID tag on eachindividual item. In retail, item tracking with RFID tags can be used inconjunction with other technologies such as bar code scanning andpayment terminals. Item tracking with RFID tags can be used in lossprevention systems by placing an RFID tag into merchandise items andplacing sensors at exit points. If an exit sensor detects a tagged itemwith a tag, which was not deactivated at the checkout, an alarm can gooff.

In another aspect, RFID tag 101 can employ one or more signal modulationmethods, including amplitude modulation, frequency modulation, phasemodulation, amplitude shift keyed modulation (ASK), phase shift keyedmodulation (PSK), and frequency shift keyed modulation (FSK). A skilledartisan would appreciate the fact that other modulation methods arewithin the spirit and the scope of the invention.

In amplitude and ASK modulation schemes, the information to betransmitted by an RFID tag is encoded by changes in the amplitude of thecarrier wave. In a frequency modulation scheme, the information to betransmitted by an RFID tag is encoded by changes in the frequency of thecarrier wave sent. In an FSKM modulation scheme, the information to betransmitted by an RFID tag is encoded by changes between two or morefrequencies of the carrier wave. In phase and PSK modulation schemes,the information to be transmitted by an RFID tag is encoded by changesin the phase of the carrier wave.

In one embodiment, an RFID tag can transform and transmit back thecarrier wave transmitted by an RFID reader. In another embodiment, anRFID tag can produce its own carrier wave.

In another aspect, RFID tag 101 can encode the information to betransmitted (payload) using an error correction protocol. In oneembodiment, an error correcting code can be calculated based on thepayload content, and appended to the payload by the RFID tag. An RFIDreader can apply the same error correction protocol to the payload andcompare the resulting calculated error correction code value with theerror correction code value received as part of the transmission. If thetwo values match, the data has been received correctly. Otherwise,another read operation can be attempted.

In another aspect, the information in RFID tag 101 can be programmedduring the manufacturing process (factory programming, typicallyproducing a read-only RFID tag) or after the manufacturing process hasbeen completed (field programming). In a further aspect, the informationin RFID tag 101 can be updated dynamically when the tag is in operation.

In a further aspect, RFID tag 101 can have memory available to store theinformation. In one embodiment, RFID tag 101 can include a non-volatilememory which retains information without the need to electrically powerthe memory device. In another embodiment, RFID tag 101 can include bothread-only and programmable memory. The read-only memory can be used,e.g., to store the tag's unique serial number. In one embodiment, thememory can be provided as an integral part of the RFID chip 111.

In a further aspect, the RFID chip 111 can comprise a memory and an RFfront end, The RF front end can be used to convert high frequency RFsignals to/from base-band or intermediate frequency signals.

In another aspect, an RFID tag can be devoid of the RFID chip 111. Achipless RFID tag can reflect back a modified portion of an RFID signaltransmitted by an RFID reader. The information in a chipless RFID tagcan be encoded by the method of modifying the received RF signal beforereflecting it back to the reader.

In another aspect, the distance at which an RFID tag can be read (theread range) can be affected by a number of factors, including the signalfrequency, the antenna gain, antenna radiation pattern, the orientationand polarization of the RFID reader antenna and the RFID tag antenna.

In one embodiment, the antenna 121 of FIG. 1 can be made of ametamaterial (MTM). Metamaterials are artificial composite materialsengineered to produce a desired electromagnetic behavior which surpassesthat of natural materials. MTM-based objects can include structureswhich are much smaller than the wavelength of electromagnetic wavespropagating through the material. MTM technology advantageously allowsfor precise control of the propagation of electromagnetic waves in theconfines of small structures by determining the values of operatingparameters which can include operating frequency, bandwidth, phaseoffsets, constant phase propagation, matching conditions, and number andpositioning of ports.

In one aspect, an MTM antenna can be physically small as compared toother types of antennas: an MTM antenna can be sized, for example, onthe order of one tenths of a signal's wavelength, while providingperformance equal to or better than an antenna made of a conventionalmaterial and sized on the order of one half of the signal's wavelength.Thus, for a frequency range of 860 MHz-930 MHz, an antenna made of aconventional material should have the size of approximately 165 mm for adipole antenna (or 82.5 mm for a monopole antenna), while a MTM antennacan have a size of 33 mm.

The ability of an MTM antenna to produce a desired electromagneticbehavior can be explained by the fact that while most natural materialsare right-handed (RH) materials (i.e. propagation of electromagneticwaves in natural materials follows the right-hand rule for the trio (E,H, β), where E is the electrical field, H is the magnetic field, and βis the phase velocity) exhibiting a positive refractive index, ametamaterial due to its artificial structure can exhibit a negativerefractive index and follow the left-hand rule for the trio (E, H, β). Ametamaterial exhibiting a negative refractive index can be a pureleft-handed (LH) metamaterial by simultaneously having negativepermittivity and permeability. A metamaterial can combine RH and LHfeatures (Composite Right and Left Handed (CRLH) materials), In oneembodiment, the antenna 121 of FIG. 1 can have a Composite Right andLeft Handed (CRLH) structure.

In one embodiment, an RFID tag 101 of FIG. 1 can comprise an antenna 121provided by a patch cell 210 a, 210 b (best viewed in FIG. 2). A patchcell 210 a can further comprise a metal patch 220 a suspended over theground plane 220 b. An equivalent circuit diagram 240 a can include acombination of series inductance 242 a, 244 a and a shunt capacitance246 a.

In another embodiment, a patch cell 210 b can further comprise a metalpatch 230 a connected to the ground plane 230 b through a via 235. Inone embodiment, the diameter of the via can be adjustable depending onthe required antenna parameters. An equivalent circuit diagram 240 b caninclude a combination of series inductance 242 b, 244 b, a shuntinductance 245, and a shunt capacitance 246 b.

In another embodiment, the antenna 121 of FIG. 1 can comprise a patchcell array 311 (best viewed in FIG. 3) including two or more 1-D or 2-Dpatch cells 321 a, 321 b disposed horizontally in a plane parallel tothe patches. Each top patch of the cell can be connected to a groundplane 331 through a via 335 a, 335 b. An equivalent circuit diagram 340can include two or more inductance groups 341 a, 341 b. Each inductancegroup 341 a, 341 b can comprise two or more inductances connected inseries. The inductance groups 341 a, 341 b can be connected in serieswith a capacitance 343. The equivalent circuit diagram 340 can furthercomprise two or more shunt capacitances 346 a, 346 b. The equivalentcircuit diagram 340 can further comprise two or more shunt inductances345 a, 345 b.

In a yet another embodiment, antenna 121 of FIG. 1 can comprise a patchcell stack 410 (best viewed in FIG. 4) including two or more 1-D or 2-Dpatch cells 420 a, 420 b disposed vertically in a plane perpendicular tothe patches. The bottom patch of each cell can be connected to a groundplane. An equivalent circuit diagram 440 can include two or morecapacitances 441 a, 441 b connected in series with an inductance 443.The equivalent circuit diagram 440 can further comprise two or moreshunt inductances 446 a, 446 b.

In another aspect, the antenna gain (i.e., the relation of the intensityof an antenna in a given direction to the intensity that would beproduced by a hypothetical ideal antenna that radiates equally in alldirections and has no losses) can increase with increasing the number ofthe patch cells.

While the size of a patch cell made of a conventional material can beapproximately one-half of the signal wavelength, the size of a patchcell made of a metamaterial can be reduced to approximately one-tenth ofthe signal wavelength. Electromagnetic metamaterials can be synthesizedby embedding various constituents with novel geometric shapes such astransmission line and split ring resonator into some host media.

A transmission line can combine series capacitance (CO and shuntedinductance (L_(L)), and can have the left-hand properties which cansupport backward wave with propagation phase constant. Since pureleft-hand transmission line does not exist due to parasitic right-handcapacitors (C_(R)) and inductors (L_(R)) occurring in fabricationprocesses, a realizable transmission line approach can be a CompositeRight/Left-hand (CRLH) transmission line with propagation phase constantβ shown in FIG. 5. At low frequencies a CRLH transmission line cansupport a backward wave showing left-hand properties, while at highfrequencies it can support a forward wave showing right-hand properties.A CRLH transmission line can exhibit properties not dependant uponresonance, and can have low loss and broad band performance.

A split ring resonator (SRR) can be provided by a nonmagnetic conductingunit made of metal like copper. In one embodiment, a SRR can be providedby a pair of concentric annular rings separated by a small gap, withsplits in them at opposite ends. A magnetic flux penetrating the metalrings can induce rotating currents in the rings, which can produce theirown flux to enhance or oppose the incident field. Because of the splitsin the rings, the structure can support resonant wavelengths much largerthan the diameter of the rings. The small gaps between the rings canproduce large capacitance values which lower the resonating frequency,therefore the dimensions of the structure can be small compared to theresonant wavelength. The resonance frequency of a SRR can depend on itsgeometrical parameters.

An SRR can be provided in one of a variety form factors, including rodsplit rings, nested split rings, single split rings, deformedsplit-rings, spiral split rings, extended S-structures, etc. FIG. 6depicts two examples of nested split ring resonators 610 a, 610 b.

In another aspect, antenna 121 of FIG. 1 can support two or moreoperational frequency bands tailored to specific applications and notlimited to harmonic frequency multiples. A frequency band can becharacterized by its central frequency. In one embodiment, the size ofantenna 121 of FIG. 1 can be less than or equal to one tenth of amaximum of the center frequencies for the frequency bands supported bythe antenna.

In a further aspect, an MTM-based component (e.g., a broadband matchingcircuit, a phase-shifting component, or a transmission line) canpreserve phase linearity over frequency ranges which are five to tentimes greater than those provided by components made of conventionalmaterials.

In another embodiment, there is provided an encoded information reading(EIR) terminal for incorporation in a data collection system. The datacollection system, schematically shown in FIG. 7, can include aplurality of EIR terminals 100 a-100 z in communication with a pluralityof interconnected networks 110 a-110 z. In one aspect, the plurality ofnetworks 110 a-110 z can include at least one wireless communicationnetwork.

In a further aspect, an EIR terminal can comprise a communicationinterface which can be used by the terminal to connect to one or morenetworks 110 a-110 z. In one embodiment, the communication interface canbe provided by a wireless communication interface.

The EIR terminal 100 c can establish a communication session with thehost computer 171. In one embodiment, network frames can be exchanged bythe EIR terminal 100 c and the host computer 171 via one or morerouters, base stations, and other infrastructure elements. In anotherembodiment, the host computer 171 can be reachable by the EIR terminal100 c via a local area network (LAN). In a yet another embodiment, thehost computer 171 can be reachable by the EIR terminal 100 c via a widearea network (WAN). A skilled artisan would appreciate the fact thatother methods of providing interconnectivity between the EIR terminal100 c and the host computer 171 relying upon LANs, WANs, virtual privatenetworks (VPNs), and/or other types of network are within the spirit andthe scope of the invention.

In one embodiment, the communications between the EIR terminal 100 c andthe host computer 171 can comprise a series of HTTP requests andresponses transmitted over one or more TCP connections. In oneembodiment, the communications between the ER terminal 100 c and thehost computer 171 can comprise VoIP traffic transmitted over one or moreTCP and/or UDP ports. A skilled artisan would appreciate the fact thatusing other transport and application level protocols is within thescope and the spirit of the invention.

In one aspect, at least one of the messages transmitted by the EIRterminal can include decoded message data corresponding to, e.g., a barcode label or an RFID label attached to a product or to a shipment item.For example, an DR terminal can transmit a request to the host computerto retrieve product information corresponding to a product identifierencoded by a bar code label attached to the product, or to transmit anitem tacking record for an item identified by a bar code label attachedto the product.

In another aspect, the FIR terminal 100 can further comprise at leastone microprocessor 310 and a memory 320, both coupled to the system bus370, as best viewed in FIG. 8. The microprocessor 310 can be provided bya general purpose microprocessor or by a specialized microprocessor(e.g., an ASIC). In one embodiment, the EIR terminal 100 can comprise asingle microprocessor which can be referred to as a central processingunit (CPU). In another embodiment, the EIR terminal 100 can comprise twoor more microprocessors, for example a CPU and a specializedmicroprocessor (e.g., an ASIC). In one embodiment, the memory 320 can beprovided by RAM, ROM, EPROM, and/or SIM card-based memory.

The EIR terminal 100 can further comprise one or more encodedinformation reading (FIR) devices 330, including a bar code readingdevice, an RFID reading device, and a card reading device, also coupledto the system bus 370. In one embodiment, an EIR reading device can becapable of outputting decoded message data corresponding to an encodedmessage. In another embodiment, the EIR reading device can output rawmessage data comprising an encoded message, e.g., raw image data or rawRFID data.

Of course, devices that read bar codes, read RFID, or read cards bearingencoded information may read more than one of these categories whileremaining within the scope of the invention. For example, a device thatreads bar codes may include a card reader, and/or RFID reader; a devicethat reads RFID may also be able to read bar codes and/or cards; and adevice that reads cards may be able to also read bar codes and/or RFID.For further clarity, it is not necessary that a device's primaryfunction involve any of these functions in order to be considered such adevice; for example, a cellular telephone, smartphone, or PDA that iscapable of reading bar codes is a device that read bar codes forpurposes of the present invention

The EIR terminal 100 can further comprise a keyboard interface 354, adisplay adapter 355, both also coupled to the system bus 370. The EIRterminal 100 can further comprise a battery 356.

In one embodiment, the EIR terminal 100 can further comprise a GPSreceiver 380. In one embodiment, the EIR terminal 100 can furthercomprise at least one connector 390 configured to receive a subscriberidentity module (SIM) card.

As noted herein supra, in one embodiment, EIR terminal 100 can comprisean RFID reading device 333. In a further aspect, the RFID reading devicecan comprise an antenna 338.

In one embodiment, the antenna 338 of FIG. 8 can have a Composite Rightand Left Handed (CRLH) structure.

In one embodiment, the antenna 338 of FIG. 8 can be provided by a patchcell 210 (best viewed in FIG. 2). A patch cell 210 a can furthercomprise a metal patch 220 a suspended over the ground plane 220 b. Anequivalent circuit diagram 240 a can include a combination of seriesinductance 242 a, 244 a and a shunt capacitance 246 a.

In another embodiment, a patch cell 210 b can further comprise a metalpatch 230 a connected to the ground plane 230 b through a via 235. Inone embodiment, the diameter of the via can be adjustable depending onthe required antenna parameters. An equivalent circuit diagram 240 b caninclude a combination of series inductance 242 b, 244 b, a shuntinductance 245, and a shunt capacitance 246 b.

In another embodiment, the antenna 338 of FIG. 8 can comprise a patchcell array 311 (best viewed in FIG. 3) including two or more 1-D or 2-Dpatch cells 321 a, 321 b disposed horizontally in a plane parallel tothe patches. Each top patch of the cell can be connected to a groundplane 331 through a via 335 a, 335 b. An equivalent circuit diagram 340can include two or more inductance groups 341 a, 341 b. Each inductancegroup 341 a, 341 b can comprise two or more inductances connected inseries. The inductance groups 341 a, 341 b can be connected in serieswith a capacitance 343. The equivalent circuit diagram 340 can furthercomprise two or more shunt capacitances 346 a, 346 b. The equivalentcircuit diagram 340 can further comprise two or more shunt inductances345 a, 345 b.

In another embodiment, the antenna 338 of FIG. 8 can comprise a patchcell stack 410 (best viewed in FIG. 4) including two or more 1-D or 2-Dpatch cells 420 a, 420 b disposed vertically in a plane perpendicular tothe patches. The bottom patch of each cell can be connected to a groundplane. An equivalent circuit diagram 440 can include two or morecapacitances 441 a, 441 b connected in series with an inductance 443.The equivalent circuit diagram 440 can further comprise two or moreshunt inductances 446 a, 446 b.

In another aspect, the gain of the antenna 338 of FIG. 8 (i.e., therelation of the intensity of an antenna in a given direction to theintensity that would be produced by a hypothetical ideal antenna thatradiates equally in all directions and has no losses) can increase withincreasing the number of the patch cells.

In another aspect, antenna 338 of FIG. 8 can support two or moreoperational frequency bands tailored to specific applications and notlimited to harmonic frequency multiples. A frequency band can becharacterized by its central frequency. In one embodiment, the size ofantenna 121 of FIG. 1 can be less than or equal to one tenth of amaximum of the center frequencies for the frequency bands supported bythe antenna.

While the present invention has been particularly shown and describedwith reference to certain exemplary embodiments, it will be understoodby one skilled in the art that various changes in detail may be affectedtherein without departing from the spirit and scope of the invention asdefined by claims that can be supported by the written description anddrawings. Further, where exemplary embodiments are described withreference to a certain number of elements it will be understood that theexemplary embodiments can be practiced utilizing less than the certainnumber of elements.

A small sample of systems methods and apparatus that are describedherein is as follows:

A1. A radio frequency identifier (RFID) tag comprising:

-   -   an RFID chip; an antenna provided by at least one of: a patch        cell array comprising one or more patch cells, a patch cell        stack comprising two or more patch cells;    -   a feed line electrically coupling said RFID chip to said        antenna;    -   wherein an equivalent circuit for said patch cell array        comprises:        -   at least one inductance group comprising at least two series            inductances;        -   at least one shunt capacitance;    -   wherein an equivalent circuit for said patch cell stack        comprises:        -   at least two capacitances connected via a series inductance;        -   at least two shunt inductances; and    -   wherein said antenna has a composite right- and left-handed        (CRLH) structure.

A2. The RFID tag of A1, wherein said equivalent circuit for said patchcell array further comprises one or more shunt inductances.

A3. The RFID tag of A1, wherein said RFID chip comprises a radiofrequency (RF) front end and a memory.

A4. The RFID tag of A1, wherein said antenna is configured to supportone or more frequency bands.

A5. The RFID tag of A1, wherein said antenna is configured to supportone of more frequency bands, each frequency band of said one or morefrequency bands having a center frequency; and

-   -   wherein said antenna has a size of less or equal to one tenth of        a maximum of said center frequencies.

A6. The RFID tag of A1, wherein said feed line is provided by one of: amonopole, a micro metal stripe, a coaxial cable, a twin parallel wire, acoplanar waveguide.

A7. The RFID tag of A1, further comprising a battery.

A8. The RFID tag of A1, wherein said patch cell array comprises two ormore patch cells;

-   -   wherein said at least one inductance group is provided by two or        more inductance groups connected via a series capacitance; and    -   wherein said at least one shunt capacitance is provided by two        or more shunt capacitances.

A9. The RFID tag of A8, wherein said antenna has a gain, said gainincreasing with increasing the number of said patch cells.

A10. The RFID tag of A8, wherein each patch cell of said two or morepatch cells further comprises a patch suspended over a ground plane.

A11. The RFID tag of A8, wherein each patch cell of said two or morepatch cells further comprises a patch electrically coupled to a groundplane.

A12. The RFID tag of A8, wherein said patch cell array comprises two ormore patches electrically coupled to a ground plane.

B1. An encoded information reading (EW) terminal comprising:

-   -   a microprocessor;    -   a memory communicatively coupled to said microprocessor;    -   an EIR device selected from the group consisting of: a bar code        reading device, an RFID reading device, and a card reading        device, said EIR device configured to perform at least one of:        outputting raw message data comprising an encoded message and        outputting decoded message data corresponding to an encoded        message;    -   a communication interface;    -   wherein said RFID reading device further comprises an antenna        provided by at least one of: a patch cell array comprising one        or more patch cells, a patch cell stack comprising two or more        patch cells;    -   wherein an equivalent circuit for said patch cell array        comprises:        -   at least one inductance group comprising at least two series            inductances;        -   at least one shunt capacitance;    -   wherein an equivalent circuit for said patch cell stack        comprises:        -   at least two capacitances connected via a series inductance;        -   at least two shunt inductances; and    -   wherein said antenna has a composite right- and left-handed        (CRLH) structure.

B2. The encoded information reading (EIR) terminal of B1, wherein saidequivalent circuit for said patch cell array further comprises one ormore shunt inductances.

B3. The encoded information reading (EIR) terminal of B1, wherein saidantenna is configured to support one or more frequency bands.

B4. The encoded information reading (EIR) terminal of B1, wherein saidantenna is configured to support one of more frequency bands, eachfrequency band of said one or more frequency bands having a centerfrequency; and

-   -   wherein said antenna has a size of less or equal to one tenth of        a maximum of said center frequencies.

B5. The encoded information reading (EIR) terminal of B1, wherein saidfeed line is provided by one of: a monopole, a micro metal stripe, acoaxial cable, a twin parallel wire, a coplanar waveguide.)

B6. The encoded information reading (EIR) terminal of B1, wherein saidpatch cell array comprises two or more patch cells;

-   -   wherein said at least one inductance group is provided by two or        more inductance groups connected via a series capacitance; and    -   wherein said at least one shunt capacitance is provided by two        or more shunt capacitances.

B7. The encoded information reading (EIR) terminal of B6, wherein saidantenna has a gain, said gain increasing with increasing the number ofsaid patch cells.

B8. The encoded information reading (EIR) terminal of B6, wherein eachpatch cell of said two or more patch cells further comprises a patchsuspended over a ground plane.

B9. The encoded information reading (EIR) terminal of B6, wherein eachpatch cell of said two or more patch cells further comprises a patchelectrically coupled to a ground plane.

B10. The encoded information reading (EIR) terminal of B6, wherein saidpatch cell array comprises two or more patches electrically coupled to aground plane.

What is claimed is:
 1. A radio frequency identifier (RFID) tagcomprising: an RFID chip; an antenna provided by a patch cell stackcomprising two or more patch cells; a feed line electrically couplingthe RFID chip to the antenna; wherein an equivalent circuit for thepatch cell stack comprises: at least two capacitances, each of the atleast two capacitances connected to each additional capacitance of thetwo or more capacitances via a series inductance; and at least two shuntinductances, wherein the antenna is configured to support one or morefrequency bands, each frequency band of the one or more frequency bandshaving a center frequency, and wherein the antenna has a size of aportion of a wavelength corresponding to a maximum of the centerfrequencies.
 2. The RFID tag of claim 1, wherein the RFID chip comprisesa radio frequency (RF) front end and a memory.
 3. The RFID tag of claim1, wherein the antenna is configured to support one or more frequencybands.
 4. The RFID tag of claim 1, wherein the antenna has a size ofless or equal to one tenth of a maximum of the center frequencies. 5.The RFID tag of claim 1, wherein the feed line is provided by one of: amonopole, a micro metal stripe, a coaxial cable, a twin parallel wire, acoplanar waveguide.
 6. The RFID tag of claim 1, further comprising abattery.
 7. The RFID tag of claim 1, wherein the patch cell stackincludes two or more patch cells disposed vertically in a planeperpendicular to the patch cells.
 8. An apparatus comprising: acommunication interface; an RFID reader comprising an antenna providedby a patch cell stack comprising two or more patch cells; wherein anequivalent circuit for the patch cell stack comprises: at least twocapacitances each of the at least two capacitances connected to eachadditional capacitance of the two or more capacitances via a seriesinductance; at least two shunt inductances, wherein the antenna isconfigured to support one or more frequency bands, each frequency bandof the one or more frequency bands having a center frequency.
 9. Theapparatus of claim 8, wherein the antenna has a size less than or equalto one tenth of a maximum of the center frequencies.
 10. The apparatusof claim 8, wherein the feed line is provided by one of: a monopole, amicro metal stripe, a coaxial cable, a twin parallel wire, a coplanarwaveguide.
 11. The apparatus of claim 8, wherein the patch cell stackincludes two or more patch cells disposed vertically in a planeperpendicular to the patch cells.
 12. A radio frequency identifier(RFID) tag comprising: an antenna provided by a patch cell stackcomprising two or more patch cells disposed vertically in a planeperpendicular to the patch cells; a feed line electrically coupled tothe antenna; wherein an equivalent circuit for the patch cell stackcomprises: at least two capacitances, each of the at least twocapacitances connected to each additional capacitance of the two or morecapacitances via a series inductance; and at least two shuntinductances, wherein the antenna is configured to support one or morefrequency bands, each frequency band of the one or more frequency bandshaving a center frequency.
 13. The RFID tag of claim 12, wherein theRFID chip comprises a radio frequency (RF) front end and a memory. 14.The RFID tag of claim 12, wherein the antenna is configured to supportone or more frequency bands.
 15. The RFID tag of claim 12, wherein theantenna has a size of less or equal to one tenth of a maximum of thecenter frequencies.
 16. The RFID tag of claim 12, wherein the feed lineis provided by one of: a monopole, a micro metal stripe, a coaxialcable, a twin parallel wire, a coplanar waveguide.
 17. The RFID tag ofclaim 12, further comprising a battery.